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ALLOXANTIN                                 129
Properties.— Uric acid forms microscopic crystals of a charac-
teristic shape. It is insoluble in water, but dissolves in the
presence of many organic substances. On dry distillation it
yields ammonia, cyanuric acid, and urea.
Reactions.—Evaporate a little of the acid with a few c.c. of
dilute nitric acid to dryness on the water-bath. An orange or
red residue remains. On cooling, add ammonia. A fine purple
colour is produced (murexide test) ; see also Reaction for
alloxan (p. 130).
Alloxantin, CHH4N4O7 + 3H2O
Liebig, Wohler, Annalen, 1838, 26, 262.
to grins, uric acid.
20   „      (18 c.c.) cone, hydrochloric acid diluted with an
equal weight of water.
i\         potassium chlorate.
The hydrochloric acid is poured over the uric acid. The
mixture is heated to 35°, and the potassium chlorate, finely
powdered, is added in small quantities at a time with constant
shaking. When about two grams of the chlorate have been
added, the uric acid will have nearly dissolved, and the liquid
has a faint yellow colour. It is diluted with double its volume
of water, allowed to stand for about an hour, and filtered. The
filtrate is saturated with hydrogen sulphide, and yields,
after being left for 12 hours, crystalline crusts, often of a
reddish tint, of alloxantin mixed with sulphur. It is filtered
and washed with cold water, and the alloxantin dissolved in a
.small quantity of hot water, and filtered from the residue of
sulphur. On cooling the filtrate, colourless crystals separate
out. Yield 7—8 grams.
CflH4N4O3 + 0 + HoO « C.iH2NaO4 4- CONaH4,
Uric add.                                    Alloxan.                 Urea.
-C.iH.NoO.t 4- H,S = CRH4N4Of + S + H,O,
Properties.— Hard, colourless crystals, slightly soluble in cold4
more readily in hot water.
COHEN'S ADV. p. o. c.                                                  K